Floating body for seaplanes



June 24, 1930. I A. ROHRBACH 121976? FLOATING BODY FOR smrmms Filed April 18, 1927 Shams-Sheet l June 24, 1930. A. ROHRBACH 1,767,815

FLOATING BODY FQR SEAPL ANES Filed April 18, 1927 2 Sheets-Sheet 2 flat bottom would require solid re-inforce- Patented June '24, 1930 UNITED STATES PATENT OFFICE ADOLF ROHRIBAOH, OF BERLIN-WILMERSDORF, GERMANY, ASSIGNOR '.I'.O BOHRBACH PATENTS CORPORATION, A CORPORATION OF DELAWARE rhon'rme BODY roa smrrms Application filed April 18, 1927, Serial No.

This invention relates to seaplanes. 5

High wing-loading iniairplanes leads to very important advantages, of which the most striking are: enhanced manceuvrability, reduced structural weight and smaller ower plant, with undiminished useful loa In seaplanes, there is another im rtant advantage of the high wing loadlng and consequently reduced structural dimensions, i. e., the improved seaworthiness resulting from the reduced wind resistance of the smaller dimensioned surfaces, especiall the wing surfaces. An increase of wing loading will produce, however, several more or less serious difliculties, as, for instance, a rather highlanding speed and consequent high impact forces at landing, the latter increasing approximately with the square of the actual landing speed.

Seaplanes with high wing loading would, therefore, be expected to have rather heavy bottom and hull structures. In order to avoid this, objection, I designed my first flying-boats with narrow hulls, which were of rectangular section, i. e., flat-bottomed. The high take oil speed involved with the high wing loading produced sufficient buoyancy even with the narrow hull structures.

The ever increasing requirements which have to be met by modern flying-boats render it necessary to provide the same with wider hulls. The passengers must be seated comfortably and accommodations must be rovi-ded for two pilots sitting side by side. gvidening of the boat without altering the wing loading would, however, result in a considerably increased hull weight, as the ment, in order to be able to withstand the impact of the water while running in heavy seas or upon alighting.

In order to reduce the high impact pressures on the boat bottom the' latter has been keeled. With a view to the facilities of alighting and wave-breaking or cutting with the machine afloat on the water the chosen keel-angle should be rather small, but it must be considered, in this connection, that the resultant loss of buoyancy on the water and the fact that with a certain keel angle 184,751, and in Germany April 19, 1926.

considerable quantities of water will be thrown over the chines, will present pronounced difficulties at start, if the machine manages to take off at all.

It has been proposed to overcome the above difliculty by making the boat hulls uncommonly wide, even widening the bottom by special prominences beyond the width of the boat proper.

It has also been proposed, inthis connection, with flat keeling of the bottom, to have the bottom surfaces so sloping upwards and, near the more elevated chines, curving downwards, that the water is deviated downwards. If this arrangement is provided in the nose portion of the boat only, with a view to avoiding the-throwing up of spray vgater, it will not avoid the indicated obsta- 0 es.

A satisfactory'hull shape, however, is also not obtained by providing the above arrangements in the rear portion of the bow, for example, in proximity to the first step, since the keeling is not sufiiciently pronounced to cleave the waves, when alighting and in high seas. Another detrimental feature of the lateral prominences is that they will be more or less completely immersed with increasing load, which means reduced lateral stability and poor take off qualities.

Even with regard to their aero-dynamical properties these rominences do not commend themselves. avorably, as they will entail air resistances increasing with the square of the flying speed and will prove the more detrimental, as the machines in question are all of the high speed type. They add considerably to the weight of bottom and hull and accordingly impair the load above indicated objections are obviated. 1 It resides in a seaplane having a floating body which is provided, substantially in the v1- cinit of the part containing the center of disp acement, with a pronounced keel and the bottom surfaces sloping upwardly therefrom and.finally' curving downwardly, so that the chines are located at a considerably higher level than the keel but substantially lower than the vertices of the curvatures, and preferably the bottom of the boat 1s not wider than the floating body hull, wlth the latter having side walls which run substantially in a straight line without pronounced break from the bottom up to the deck.

This permits of the development of the bottom so that the best possible condltions of take off andalighting are produced without increased dead load, with the width of the floating body being accommodated to the prevailing requirements and retaining the stream-lined hull shape with the side Walls carried straight upwards from the chines.

Aircraft designers have. not heretofore recognized the possibility of using a bottom shape, which, cutting and turning off the water, at the first step particularly, the latter "being the last part to emerge and in landing hitting the water first and most violently, is of equal width as the hull proper. They all feared that the keeled bottom, turning off the water, would not produce sufficient buoyancy to obtain a good start.

The accompanying drawing shows, by way of example, several embodiments of the invention.

Fig. 1 is the nose portion of a flying boat in side elevation.

Fig.2 represents .the central portion in front elevation.

Fig. 3 shows the boat body in side elevation, on an enlarged scale.

Figs. 4 and 5 are front and rear views respectively of the boat body with drawn in bulkheads, on a rather more enlarged scale.

Fig. 6 is a rear view of a somewhat modified form'of construction of the boat body.

Fig. 7 shows a stabilizing float, arranged in close proximity to the boat body, in side elevation and on rather enlarged scale.

1Figs. 8 and 9 are appertaining bulkhead p ans.

Figs. 10 and 11 show another flying boat developed according to the present invention, in side-- and front-elevation.

Fig. 12 shows a side elevation of a stabilizing float, on a considerably enlarged scale.

Figs. 13, 14, 15 are sections on lines iTQIIIEXIII, XIV --XIV' andXVXV of The flying boat as represented in Figs. 1-6 has a boat body a of a pronounced eeling, i. e., the bottom surfaces slope upvided with a high and slightly forwardly inclined stem. At thebow-extremity the bottom surfaces forming an acute keel-angle are chamfered and concaved. Towardsthe rear the bow isbordered by a step. Here the bottom surfaces of the how a form an.

angle of average size, merging from the keel 6 over a long stretch in the direction of the vertical side walls a. In the vicinity of the chines c which are located higher than the keel b the bottom surfaces merge into a concavity, this latter being formedby channels e which are located higher than the chines and open towards the bottom; from the said channels the water is deflected downwards. This concave part of the bottom begins at or in the vicinity of the first step and merges gradually towards the bowextremity at water level, as schematically indicated by the bulkheads plans in Fig. 4.

round keeling, that the water is more easily cut and the hull structure simplified.

' Adjacent to the first step is the central portion of the boat a the keel of which is bent so as to directly pass into the keel b of the bow a. The bottom surfaces of the part a are somewhat twisted. Their frontal border edges, near the first step, merge, from the keel line to the points d, with the rear edges of the bow bottom, and from there pass on slightly curved to the lateral walls. a, which are carried straight upwards from the chines and running through to the deck without any pronounced break. This arrangement results in a break f, aft and above the chines 0 which causes the water, running along the deviating curves e of the bow bottom, to divide. The rear edges 9, arranged near the second step h, of the bottom surfaces of the central portion of the boat a, run straightlined. The keel angle formed by them is of larger size than that formed by the front edges of the central bottom i a is the stern portion, the bottom surfaces of which are flush and set ofl against the centralportion a b means of the step 71, over the whole brea th of the bottom.

The dotted line In in Fig 3 indicates, that the keel b of the central portion a can be carried straight on to the first step, ending above the bow keel 6 This arrangement results in a remarkably pronounced first step ma over the whole breadth of the boat body, with the bottom of portion a provid- 'ing a somewhat curved shape. I

he bottom shape accordlng to the present invention has the effect, that the bottom water, causing gra ual immersion of the boat body. Thus landing without dangerous shocks is assured.

At take off the waters tossed up and following the inclined bottom surfaces of the bow, are turned off downward by the bottom curves 6 near the chines 0 thus causing suflicient dynamic buoyancy of the boat. At the break 7 the turned down water lacks a guidance: it easily separates from the bottom. The water running along the central portion a near the keel b breaks off at the second step ii.

The transition of the bottom portions of bow a and central portion a by meansof a'simple bend of the keel line at the first step, has the advantage, that the air flow is not interrupted during flight. The small eddy caused by the small break 7 is of no consequence and can practically be altogether neglected. The steph between cen-' -tral portion a and stern a has no particularly impairing effect on the air flow, since the bottoms of both portions are arranged to the rear'and upwards.

Under special circumstances it may be required, notwithstanding the deviation of the water, to provide a break at the first step over the whole breadth of the boat. This case is represented in Fig. 6. Instead'of simple inclined bottom surfaces more or less curved ones may be used for the parts a and a i are the floats used on flying boats and arranged in close proximity of the boat body. In the state, of rest they are con siderably immersed, thus producing dynamic buoyancy. In order to ensure a good dynamic buoyancy effect, the floats, in their part containing the centre of displacement, are provided with bottoms sloping down toward the keel line and again curving down beyond the chines, whereas, at the stern, they end in flush and even surfaces. The water deviating effect of these stabilizing floats is. essentially the same, as of the boat body proper.

According to the form of construction of Figs 10 and 11, representing a flying boat body a, the keel line is interrupted at both steps. The bottom surfaces of the central portion a are, to a great extent, flush and provide a larger keel angle than the inclined flush parts of the bow bottom. Near the first step the bottom surfaces of the part 0 indicated in Fig. 11 by dotted lines, are arranged tangentially to the curve 3 of the deviating surfaces of the how (1?, so that in addition to the breaks f aft of the chines 0 sharp breaks n are produced near the keel 6 which, in many cases. will succeed to break off the water current. The said arrangement oflers the advantage. that bulkheads of most simple design can be used even for the bottom parts of the central portion (1 which are arranged adjacent to the first step. 1

Another improvement of this arrangement consists in having the bow-portion p which is located directly in front of the first step extended downwardly for a short distance, one advantage, apart from-a very etficient buoyancy, being that the water is caused to more rapidly break oil so that the extensions f, n can be of smaller size. Another such downward extension of the bottom surfaces prevails at '0 at the second step between the boat parts a and (1 With this embodiment the keels b and b and the chines and c are running either perfectly or nearly straight.

The lateral stabilizing floats 7'- are improved by being provided over their whole length with water deviating bottom surfaces q, the chine edges of which occupy a more elevated position than the keel. This arrangement results in considerably increased dynamic buoyancy and improved landing properties. This new bottom shape compares favourably with the hitherto known ones by completely avoiding the throwing up of spray water.

Another improved feature of the lateral floats consists in that they are provided with cruiser-like bow and high stem; The deck 8 is flush or slightly curved and in most cases of equal breadth as the bottom so that, over a large part of the float length, no water can overfloodit. The lateral floats are preferably formed with a flat ended stern. thus there forming a terminal surface serving as a step.

The invention can be applied. with equal profit, to the floats of float-machines and flying boats.

What I claim is:

1. In a hydroaeroplane capable of flightand taking off and alighting upon the water, a floating and hydroplaning body having in the vicinity of the center of displacement a step and a pronouncedly keeled bottom which is not of substantially greater width than said body and which, is laterally curved between the keel and the chines to form concavebottom parts on both sides of the keel for a considerably lon stretch in the vicinity of the chine with t e chines located at a higher level than the keel but lower than the vertices of the concave curvatures, said pronouncedly keeled and chi-lied bottom parts extending from the step forwardsand ending somewhat above the floating line and being adapted to cleave the water when the hydroplane is alighting and. starting and said concave parts being adapted to create a cushioning effectin alighting and a reaction effect in starting.

2. An aircraft of the character set forth in claim 1 wherein the bow of the floating and hydroplaning body is cruiser shaped and provided with a high stem, the side walls of said body extending vertically upwards from the chines to the deck withoutsharp steps.

3. An aircraft of the character set forth in claim 1 wherein the floating and hydroplaning body has directly in front of the step a V-shaped bottom at the keel with the V-part merging into the concave bottom parts nearer the chines extending from the step forwards.

4. In a, hydroaeroplane capable of flight and taking off and ali hting upon the water, a floating and hydrop aning body having in the vicinity of the center of displacement a step and a bottom which is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel on a considerable stretch near the chines, with the chines located at a higher level than the keel, but lower than the vertices of the concave curvatures, the concave bottom surfaces beginning at the step and ending towards the front at the level of the waterline, said bottom surfaces being V-shaped at the keel with the bottom lines thereof substantially straight and graduall diverging outwardly, said bottom lines gra ua-lly merging into the concave art, the portion of the floating and hydrop aning body, which is located aft of the step, lying at a higher level than said step.

5. In a hydroaeroplane capable of flight and taking off and alighting upon the water, a floating and hydroplaning body provided in the vicinity of the center of displacement with a bottom which is laterally curved between the keel and the chines to form on a considerably long stretch in the vicinity of the chine concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures the floating and hydroplaning body being rovided with a step underneath the center 0 gravity of the craft with the downwardly curved bottom chine part beginning at this step and extending forward to a point above the water line, the bow being cruiser-shaped and provided with a high stem, the aft of the step portion of the floating and hydroplaning body lying at a higher "level than the step.

6. In a hydroaeroplane capable of flight.

and taking off and allghting upon the water, a floating and hydroplaning body rovided in the vicinity of the center of disp acement' with a bottom which is laterally curved between the keel and the chines to form concave bottom parts on a considerably long vided with a step substantially beneath the.

center of gravity of the craft with the downwardly curved chine structure beginning at this step and extending forward to the vicinity of the bow-top and to a point above the water line, the bow being cruiser-shaped and provided with a high stem, the side walls of the bow running from the chines to the deck without acute interruption the bottom surfaces which are located behind the step having a higher elevation than those located in front of the step, whereby the step is (pontinuous throughout the width of the 7. In a hydroaeroplane, a floating and hydroplaning body having in the vicinity of v gravity, the concave bottom structure begin-- ning at this step and ending somewhat in front at the level of the floating line, floating and hydroplaning body forming the central floatof the craft and the craft being provided with two auxiliary displacement and hydroplaning floats arranged close to the central float, and each of said auxiliary floats having a bottom in the vicinity of the center of displacement and the center of gravity thereof which is laterally curved between the keel and the chines in the vicinity of the latter to form concave bottom parts on both' sides of the keel on a considerable stretch with the chines located at a higher level than the keel, but lower than the vertices of the concave curvatures.

8. In a hydroaeroplane, a floating and hydroplaning body having in the vicinity of the center of displacement a bottom which is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel in the vicinity of the chines, with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures, the bottom of said floating and hydroplaning body having beneath the center of displacement a bending, the bottom surfaces aft of the said bending running substantially straight in the direction of the chine and sloping upwards towards the stern, said bending at the chines merging into triangular extensions forming the step of the body.

9. In a hydroaeroplane, a floating and hydroplaning body having in the vicinity of the center of displacement a bottom which is laterally curved between'the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures, a step beneath the center of gravity, the concave bottom surfaces extending from that step forwards and ending there, the floating and hydroplaning body forming the central float of the craft and the craft being provided with auxiliary displacement and hydroplaning floats arranged close to the central float, each of said auxiliary floats having a bottom in the vicinity of the center ofdisplacement and the center of gravity thereof which is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curva- 7 least one bottom step, chines tures, and the bottoms of certain of said floating bodies being ronouncedly keeled and the bottom lines of said bodies making an acute angle with each other and taking a substantially straight course outward for a certain distance and then merging into the concave surfaces.

10. In a hydroaeroplane, a floating and hydroplaning body having in the vicinity of the center of displacement a bottom which is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures, a step beneath the center of gravity, the concave bottom surfaces extending from that step forwards and ending there, the floating and hydroplaning body forming the-central float of the craft and the craft provided with auxiliary displacement and hydroplaning floats arranged close to the central float, and each of said auxiliary floats having a bottom which is throughout its length laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel, but lower than the vertices of the concave curvatures.

11, In a hydroaeroplane a floating and hydroplaning body having in the vicinity of the center of displacement a bottom w ich is laterally curved between the keel and the chines in the vicinity of the latter, to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures the floating an hydroplaning body being provided with at the downwardly curvbeginning at such step and extending forwardly therefrom, the bottom surfaces which are located behind saidstep being substantially planar and forming a !-bottom at the keel with a substantially larger angle than the bottom surfaces forward thereof, thereby forming sharp triangular surfaces at the step both at the chines and at the keel.

' 12. In a hydroaeroplane a floating and hydroplanin body having in the vicinity of the center 0% displacement a bottom which is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel at the chines with the chines located at a higher level than the ,keel but lower than the verticcs of the concave curvatures the floating and hydroplaning body being provided with at least two steps, the downwardly curved chine construction beginning at the first step and extending forwardly, the keels and the chines which are located between the two steps and behind the second step being in the mainsubstantially straight, and located higher than the first step the rearward ends of the keels and the chines and similarly the bottom surfaces joining the keels and the chines being curved downwards.

13. In a hydroaeroplane, a floating and hydroplaning body having beneath the center of displacement a step and apronounced-. ly keeled bottom which is laterally curved between the keel and the chines in the vicinity of the latter to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures, the concave bottom surfaces beginning at the step and merging into the bow-extremity, said body having at its bow side walls extending upwards from the chines to the deck without sharp steps or breaks, the bottom of the body being V- shaped at the keel'with the V-part merging gradually into the concave bottom parts nearer the chines, the bottom part aft of the step sloping upwards towards the stern.

14. An aircraft of the character set forth in claim 13, wherein the bow of the'floating and hydroplaning body is sharply edgeshaped in ground plan and provided with a high stem. 1

15. An aircraft of the character set forth in claim 1, with the bottom lines of the bow from the keel on being substantially straight at the beginning and gradually diverging outwardly toform a pronounced keeling and then gradually merging into the concave part, the bow of the body having side-walls extending in a substantially straight manner vertically upwards from the chines to the d deck.

16. A hydroaeroplane of the character set forth in claim '1 wherein the part of the body lying behind said step rises towards the stern of the body.

17. A hydroaeroplane of the character set forth in claim 1, wherein the side walls of so I 'rising towards the stern of the body:

65 side walls said body extend vertically upwards from the chines to the deck without sharp steps, the part of the body lying behind said step 18. (An aircraft of the character set forth inclaim 1 wherein the bow ending sharply edge-shaped in ground section and provided with a high stem, the sidewalls of said body extending vertically upwards from the 10 chinesto the deck without sharp steps, the

part of the body lying behind said step rismgtowards the stern of the body.

19. An aircraft of the character set forth in claim 1, wherein the floating and hydroplaning body forms the central float of the craft and the craft is provided with auxiliary displacement and hydroplaning floats arranged close to the central float, .and each of said auxiliary floats having a bottom which, in the vicinity of the center of displacement and the center of gravity thereof, is laterally curved between the keel and the chines in the vicinity of the latter to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel, but lower than the vertices of the concave curvatures, the side walls of said auxiliary floats extending vertically upwards from the chines to the deck without sharp steps.

20. An aircraft of the character set forth in claim 1 wherein the floating and hydroplaning body forms the central float of the craft and the craft is provided with auxiliary displacement and hydroplaning floats arranged close to the central float, and each of said auxiliary floats having a bottom which, in the vicinity of the center of displacement and the center of gravity thereof,

1s laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel, but lower than the vertices of the concave curvatures, the

how of said auxiliary floats being cruisershaped and provided with a high stem, the side walls of each auxiliary float extending vertically upwards from the chines to the deck.

21. Ina hydroaeroplane, a floating and hydroplaning body having in the vicinity cave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures, said body being proauxiliary displacing and hydroplaning float vided with a step underneath the center of gravity of the craft with the downwardly curved bottom chine beginning at this step and ending at a point above the water-line towards the front, the bow being cruisershaped and provided with a high stem, the

said body extending vertically in claim 1 wherein the floatin provided with auxiliary displacement and hydroplaning floats arranged close to the central float, and each of said auxiliary floats having a bottom which, in the vicinity of the center of displacement and the center of gravity thereof, is laterally curved between the keel and the chines to form concave bottom parts on both sides of the keel with the chines located at a higher level than the keel but lower than the vertices of the concave curvatures.

22. A hydroplane of the character set forth in claim 21 wherein the bottoms of the auxiliary floats throughout their length are laterally curved between the keel and the chines to form said concave bottom parts on both sides ofthe keel.

23. A hydroaeroplane of a character set forth in claim 1 the floating and hydrothan the vertices of the concave curvatures as the step is approached.

24;. A hydroaeroplane of the character set forth in claim 12 the floating and hydroplaning body having a sharply keeled V- bottom from the bow rearwardly to a point in the vicinity of the center of displacement, the sides of the V-bottom gradually assuming a more pronounced downward concavity near the chines as the center of displacement is approached with the chines located at a higher level than the keel but substantially lower than the vertices of the concave curvatures. I

25. An aircraft of the character set forth in claim lwherein the pronouncedly keeled and concaved bottom parts extend from the step to the vicinit of the bow-extremity, the sidewalls of t is front portion of the floatin body running without sharp breaks from t e chines onto the deck.

26. An aircraft of the character set forth in claim 1 wherein in the vicinity of the bowstep the proportion of the level difference of keel and chine to the reciprocal distance of the chine edges is about 1: 6.

27. A craft of the character set forth in claim 1 wherein the floating and h drolaning body forms the boat hull of a ing boat, said boa-t hull having on either si e an adapted to increase the hydro-dynamical and hydrostatical effect of the boat body.

28. An aircraft of the character set forth and hydroplaning body forms the centra float of the craft, said craft being provided with auxiliary displacing and hydroplaning floats on either side near to the central float, either of the said auxiliary floats having a bottom which, in the vicinity of the center of displacement and the center of gravity is curved laterally between keel and chines in the vicinity of the latter, to form on both sides of the keel concave bottom parts with chines located at a higher level than the 10 keel but lower than the vertices of the concave curvatures, the side walls of the said auxiliary floats running vertically upwards without sharp steps from the chines to the deck, said auxiliary floats provided with a flat and broad stern.

29. An aircraft of the character set forth in claim 21 the side walls of the said auxiliary floats extending from the chines to the deck vertically upwards without sharp steps.

4 30. An aircraft of the character set forth in claim 21, the bow of said auxiliary floats being cruiser-shaped and provided. with a high stem, the side walls of either auxiliary 25 float extending vertically upwards from the chines to the deck. 7

31. An aircraft of the character set forth in claim 21, the bow of said auxiliary floats being cruiser-shaped and provided with a high stem, the side walls of either auxiliary float extending vertically upwards from the chines to the deck, thestern of the auxiliary floats ending flat and being of broad structure.

32. A hydroaeroplane of the character set forth in claim 21, wherein the bottom of the auxiliary floats is laterally curved over their whole. length between the keel and the chines to form, on both sides of the keel, the said concave bottom parts, the auxiliary floats being provided with cruiser-shaped bow and with a high stem, their side walls extending vertically upwards from the chines to the deck, the stern being of wide structure and endingflat.

33. A hydroaeroplane of the character set forth in claim 11, wherein the portion of the bow bottom-lying directly in front of the said step is lowered on a short length.

In testimony whereof, I have signed my name to this specification.

DR. ADOLF ROHRBACH. 

